BDS Power Systems and Standby Powering 1 — Questions and Answers
Question 1: What is the typical AC voltage range used to power active components in an HFC outside plant?
- 60-90V AC (Correct answer)
- 30-40V AC
- 110-120V AC
- 220-240V AC
Correct answer: 60-90V AC
HFC outside plant equipment is powered by 60V or 90V AC delivered through the coaxial cable by power supplies, enabling remote powering of amplifiers and nodes.
Question 2: What is the primary function of a power inserter in an HFC network?
- To couple AC power onto the coaxial cable without disrupting the RF signal path (Correct answer)
- To boost signal levels at node locations
- To convert DC power to AC for customer equipment
- To protect equipment from power surges
Correct answer: To couple AC power onto the coaxial cable without disrupting the RF signal path
A power inserter couples AC plant voltage onto the coaxial cable while simultaneously passing RF signals, allowing remote powering of active equipment.
Question 3: What type of battery is most commonly used in cable plant standby power supplies?
- Lithium-ion
- Nickel-cadmium
- Valve-regulated lead-acid (VRLA) (Correct answer)
- Alkaline
Correct answer: Valve-regulated lead-acid (VRLA)
VRLA batteries are the cable industry standard for standby power due to their sealed, maintenance-free design and reliable performance in outdoor enclosures.
Question 4: In the cable industry, what is the correct term for a power supply that delivers AC voltage to the plant while also providing battery backup during utility outages?
- Passive power unit
- Uninterruptible power supply (UPS) module
- Standby power supply (SPS) (Correct answer)
- Active voltage regulator
Correct answer: Standby power supply (SPS)
A standby power supply (SPS) is the standard cable industry term for a unit that converts utility AC to plant voltage and manages battery backup for service continuity during outages.
Question 5: What is the purpose of a transfer switch in a cable plant standby power supply?
- To regulate the output voltage to a constant level
- To automatically switch between utility power and battery backup during an outage (Correct answer)
- To balance loads across multiple battery strings
- To convert AC power to DC for battery charging
Correct answer: To automatically switch between utility power and battery backup during an outage
A transfer switch detects utility power failure and automatically switches the plant load to battery power, maintaining service continuity during outages.
Question 6: What does 'power passthrough' mean in the context of HFC cable plant powering?
- Passing RF signals through a power supply without attenuation
- Converting utility power to regulated DC for active components
- Bypassing a failed power supply using an alternate feed
- Allowing AC power to travel through passive devices to reach active downstream equipment (Correct answer)
Correct answer: Allowing AC power to travel through passive devices to reach active downstream equipment
Power passthrough enables AC plant voltage to flow through passive components like taps and splitters so that active equipment farther down the coaxial plant can receive power.
Question 7: Which of the following is a key indicator that a cable plant power supply has switched to standby (battery) mode?
- An alarm or status indication along with battery voltage appearing on the output (Correct answer)
- Increased RF signal levels at downstream amplifiers
- A drop in output frequency from 60 Hz to 50 Hz
- Complete loss of power to all downstream active equipment
Correct answer: An alarm or status indication along with battery voltage appearing on the output
When a supply switches to battery mode, it typically activates an alarm or status flag and the output voltage reflects battery voltage rather than rectified utility AC.
BDS Power Systems and Standby Powering 1
What is the typical AC voltage range used to power active components in an HFC outside plant?